The present invention relates to an electrostatic deflection circuit and method for controlling the deflection of an electronic beam in an electronic beam measuring apparatus which scans a sample by an electron beam (electronic beam) and measures minute patterns.
The electronic beam measuring apparatus such as a scanning electron microscope generates an electronic beam from an electron gun and converges it on a sample, and at the same time applies a force on this electronic beam using a deflector, scans on the sample by deflecting irradiation points and collects information of the sample, and it is used, for example, for the check of the minute circuit patterns, etc.
The electronic beam measuring apparatus is generally requested to satisfy the conditions such as to be able to obtain an image of high precision with high resolution and minimum aberration such as noise and distortion, to be able to obtain a desired magnification, to have a wide field of vision, and that the apparatus is small and its structure is simple. In the electronic beam measuring apparatus, as described above, the deflector plays an important role with regard to the deflection of the electronic beam and the scan and there are the types of electromagnetic deflector and electrostatic deflector, but as these have different characteristics they have been used separately according to the use object or the use mode. For example, the electrostatic deflector, compared with the electromagnetic deflector, has characteristics such as to be able to obtain a large amount of deflection with small size and to be able to have a high speed scan rate because a high speed deflection is possible.
Thus, conventionally a focused ion beam device (the first conventional apparatus) has been proposed in which the electrostatic deflector and the electromagnetic deflector are arranged shifted in the direction of the light axis, and which performs the scan by the ion beam by the electromagnetic deflector with high magnification and performs the scan by the ion beam by the electrostatic deflector with low magnification (for example, refer to JP-A-10-199460, paragraphs 0018-0022, FIG. 2).
Also, a focused ion beam device (the second conventional apparatus) has been proposed which is provided with an electrostatic deflector in which each deflecting factor of the deflector is divided into two parts of the upstream side and the downstream side of the ion beam, and which switches the state in which both of the deflector of the upstream side and the deflector of the downstream side are connected to the deflecting power supply and the state in which only the deflector of the downstream side is connected to the deflecting power supply (for example, refer to JP-A-2002-117796, paragraph 0025, FIG. 6).